海洋植物プランクトンの光合成特性とその生態学的意義

Abstract

Photosynthetic characteristics of marine phytoplankton were investigated in the cruises of the northwestern Pacific near Japan, and their ecological meaning in the chlorophyll method of estimating the oceanic primary production was discussed.1. The differentiation of photosynthetic pattern of phytoplankton into sun and shade types was recognized in the Kuroshio area as well as in the Oyashio area, but not in the mixed water region.2. Maximal photosynthetic rate of phytoplankton in the Oyashio area was about 3 to 5times greater than that in the Kuroshio area. In the mixed water region, the value was intermediate between these two. The absolute maximal photosynthetic rate is ecologically the most important in estimating the primary production.3. Light inhibition in photosynthesis was clearly observed for the surface sample from the Oyashio area and for the subsurface samples both in the Oyashio and in the Kuroshio where, however, a slight inhibition was observed in the surface sample. Only on a bright sunny day, the light inhibition in photosynthesis must be taken into account in the chlorophyll method.4. Temperature effect on photosynthesis could be ignored in the chlorophyll method so long as we deal with deeper waters under weakened illumination.5. The oceanic primary production can be estimated from the light-photosyn-thesis curve, the chlorophyll content in waters, and the light data. The light-photosynthesis curve should be representative to each water mass, and it might be accurate enough to calculate the primary production over a fairly vast area, because the photosynthetic rate and pattern showed no marked geographical differentiation within a water mass.